Generic callback protocols break with kwargs

I'm getting an unexpected error when using callback protocols with kwargs

Normal callback with no args or kwargs works fine:

from typing import *

T1 = TypeVar('T1')
T2 = TypeVar('T2')

T_contra = TypeVar('T_contra', contravariant=True)
T_co = TypeVar('T_co', covariant=True)

class Callback(Protocol[T_contra, T_co]):
  def __call__(self, __element: T_contra) -> T_co:
    pass

def applyit(func: Callback[T1, T2], y: T1) -> T2:
    return func(y)

def callback(x: str) -> int:
    pass

applyit(callback, 'foo')  # OK!

callback with args works fine:

from typing import *

T1 = TypeVar('T1')
T2 = TypeVar('T2')

T_contra = TypeVar('T_contra', contravariant=True)
T_co = TypeVar('T_co', covariant=True)

class CallbackWithArgs(Protocol[T_contra, T_co]):
  def __call__(self, __element: T_contra, *args: Any) -> T_co:
    pass

def applyit_with_args(func: CallbackWithArgs[T1, T2], y: T1) -> T2:
    return func(y)

def callback_with_args(x: str, *args: Any) -> int:
    pass

applyit_with_args(callback_with_args, 'foo')  # OK!

But the same thing with kwargs produces an error:

from typing import *

T1 = TypeVar('T1')
T2 = TypeVar('T2')

T_contra = TypeVar('T_contra', contravariant=True)
T_co = TypeVar('T_co', covariant=True)

class CallbackWithKwargs(Protocol[T_contra, T_co]):
  def __call__(self, __element: T_contra, **kwargs: Any) -> T_co:
    pass

def applyit_with_kwargs(func: CallbackWithKwargs[T1, T2], y: T1) -> T2:
    return func(y)

def callback_with_kwargs(x: str, **kwargs: Any) -> int:
    pass

# Argument 1 to "applyit_with_kwargs" has incompatible type "Callable[[str, KwArg(Any)], int]"; expected "CallbackWithKwargs[str, <nothing>]"
applyit_with_kwargs(callback_with_kwargs, 'foo')  # Error!

Perhaps this is expected behavior and I'm just overlooking some subtle interplay between the args in the last case, but it seems like a bug.

mypy 0.720

Exécutez le reproducteur fourni du protocole de callback avec le comportement signalé de mypy 0.720, en comparant les cas sans argument, avec *args et avec **kwargs. Suivez les chemins d’inférence de types et de compatibilité des callbacks responsables du diagnostic, puis ajoutez un test de régression montrant que le callback avec kwargs est accepté sans perdre le type de retour.